The DAIDS Immunology Quality Assessment Program (IQA) provides a critically needed resource that (1) evaluates the abilities of laboratories in the U.S. and in developing countries to accurately and reliably perform study-specified immunological tests (mainly CD4 and CD8 enumeration) and PBMC viable freezing, (2) advises and trains when deficiencies are identified, and (3) evaluates immunology-based technologies for implementation in multi-site DAIDS trials.